Main window - go to Bandwidth - click on the Minimizing icon to show longer timeframe.
Click again and again.
All of a sudden at the left side you have a dark space.
Obviously the memory of the Bandwidth is not enough.

Same issue for every single DL.
Choose a DL.  Go to bandwidth - minimize.

Funny thing is, if you do that a second time, it works.

I can see that behaviour even when it is running for 8 hours.